This invention relates to footwear and particularly to a prosthesis used "in addition to" (Webster) the plantar portion of a person's foot, it being an object of this invention to provide an orthotically correct plantar insert for foot support during normal and abnormal activities, and including athletic activities. It is also an object of this invention to provide a planar insert that supportably embraces the plantar portion of the foot in an optimum disposition for the lever function of the foot, for example in the propulsion mode.
The present invention is an improvement over and an implementation of features disclosed in my prior U.S. Pat. Nos. 4,305,212 issued Dec. 15, 1981 and 5,067,257 issued Nov. 21, 1991. U.S. Pat. No. 4,305,212 entitled ORTHOTICALLY DYNAMIC FOOTWEAR discloses a shoe incorporating dynamic Orthotic means which adapt to the foot in a prescribed manner, controlling heel "strike" and weight bearing loads, establishing a cup-shape to "catch" the heel and foot to stabilize it, balancing and maintaining the sub-talar joint in a neutral attitude and the mid-tarsal joint locked, enabling the foot and ankle so maintain optimum integrity as an efficient support and propulsion system, and resisting the symptomatic tendency for the sub-talar joint to overcompensate and overstress the anatomy. U.S. Pat. No. 5,067,257 entitled INJECTION FITTED BOOT LINER discloses a protective liner custom fitted by low pressure fluid injection over a wearer's anatomy, by permeation of select areas of porous padding, surrounding areas of nonporous padding, with an impervious membrane occluding portions of the porous padding to control fluid resin penetration and with scarfed abutment of padding for gradual softness variation, including a method by which a pair of liners are simultaneously injected with fluid resin while the wearer's anatomy is in place, for hardening of the fluid and of the permeated padding. The improvement herein lies in the implementation of a plantar insert that is incorporated or inserted into the shoe, the plantar insert being characterized by a laminate article of materials that simulate the plantar body tissue of the human foot. And further, pre-selected cushion inserts are strategically placed, especially for comfort and for protection against bony prominences, namely heel impact and metatarsal impact.
It is an object of this invention to implement the aforementioned improvements in an article of manufacture, and a method of making the same, all of which is simple and practical and with ensured results.
Numerous manipulative methods have been proposed for finding and positioning the joint processes of the foot in order to achieve a neutral sub-talar joint and locked mid-talar joint, for the purpose of molding and fabricating prosthetic footwear. Reference is made to propulsive postures created within lasted forms of track and other field event shoes, bicycle racing shoes and ice skating and ski boots, as they have been used in the recent past without underfoot prosthesis considerations. Orthotically, there is a neutral and locked alignment of the foot to be considered as the optimum centered and balanced position for bearing weight with minimal stress and fatigue. For example, research has demonstrated that there is minimum firing of muscles in maintaining balance when an optimum balanced positioning of the foot is maintained, and which is interpreted as reducing stress and fatigue.
The accepted methods of optimum foot positioning are either the unweighted (seated, prone, or supine) or the weighted (standing) positions. When unweighted the technician, that is the person in charge of implementing this insert, dorsiflexes the ankle joint against resistance by applying upward pressure to the head of the fifth metatarsal with one hand, and feels for a neutral alignment of the mid-tarsal joint under the thumb and forefinger with the other hand. When neutral is felt, the foot position is held until the molding materials catalyze, cool and cure to the shape of the foot's planar surface. When weighted, the techician positions the mid-tarsal joint, feeling again with the thumb and forefinger by rotating the shaft of the tibia inward or outward. However, displacement of soft tissue and one joint alignment becomes difficult when the foot is weighted, since with each procedure there are different displacements of tissue and bone which affect the supporting interface configurations. Accordingly, it is an object of this invention to provide a plantar insert whereby either unweighted or weighted molding methods are acceptable and highly successful, as circumstances may require.
There are various methods for applying molded materials to the foot, the most sophisticated of which uses atmospheric pressure to suck the resin materials against the foot, by sealing them off within a plastic bag and then evacuating the air with a pump.
The most commonly used molding method is the weight bearing method. The resin materials are usually counter pressed against the foot by a variety of foam shapes and densities. Another method is to insert a heated plastic sheet or foam into the shoe and allow the person being fitted to dynamically mold the plastic while it cures, as by walking about. In accordance with this invention, a plantar insert procedure is used so that the foot is positioned according to a unique biomechanical technique, whereby a technician has complete control and flexibility to use full-weight bearing, semi-weight bearing or non-weight bearing methods in attaining the required orthotic positioning and optimum supportive positioning of the prothesis.
It is an object of this invention to simultaneously mold a pair of prostheses, as thus far described, enforcing neutral and locked alignment by the pre-molded plantar inserts. This minimizes the total weight and volume of resin needed to fill the inherent spaces that occur between the plantar insert and the shoe interior, and the differences between the premolded plantar insert shape and the shape of the individual's foot in its neutral and locked alignment. Therefore, with this invention a vacuum is not necessary to suck the molding resin materials up and hold them against the foot. On the contrary, soft foot tissue is conformed to by the soft tissue simulating resin material and so that the customized molding is carried out effectively with or without weight bearing.
In accordance with this invention, it is an object that this biodynamic phenomenon is used to position and then mold the quite specific plantar shapes into the optimum position for the prosthetic foot support, while selecting the appropriate resin materials which allow for the normal adaptive motions and foot functions. It is therefore an object of this invention to provide a plantar insert for the centered and neutral position from which all movements originate and to which they return. The resulting prosthesis encourages good posture rather than poor off-balance posture that produces stress and could cause injury.